The present invention relates to strand user devices such as, for example, yarn storage and feeding systems adapted to collect or accumulate a given quantity of strand supplied from a strand source for delivery to an intermittently operating yarn consuming device and to replenish withdrawn yarn so as to maintain the accumulated quantity at a generally consistent level, and in the environment, represents improvements upon the yarn storage feeding system of the type disclosed in U.S. Pat. No. 3,776,480.
As is explained more fully in U.S. Pat. No. 3,776,480 it is known in the prior art to provide a yarn storage feeder system (which for ease of reference is sometimes referred to herein simply as a "feeder") interposed between a strand supply source and an intermittently operated strand consuming device such as a winder, knitting machine, weaving loom, or even another yarn storage feeder. Such feeders operate to accumulate a body of strand for ready and immediate delivery therefrom to the strand consuming device, the body of strand being replenished as lengths therefrom are withdrawn by the latter unit. Such feeders typically include a yarn collecting drum on which strand from a suitably supply source is wound temporarily and then removed under a controlled, uniform tension for passage to the consuming device. These feeders eliminate wide variations in yarn tension which occur when the strand is delivered over-end from a source, such as a cone or a package, and permits the strand to feed to the consuming unit at a substantially constant tension.
While the feeders of the type disclosed in the prior cited patent perform admirably in accumulating and delivering most types of strandular material, it has been found that when the strandular material in an anisotropic material such as polypropylene tape utilized for weaving carpet backing, the tape when advancing to and through the feeder tends to split or fibrillate, usually due to excessive tension caused by passing the tape stationary guides. Such fibrillation leads to problems in the downstream processing of the tape in the consuming device.
Amplifying on the problem just mentioned, it has been rather usual in the past to arrange a plurality of strand supply packages on stands proximate to the rear of each yarn storage feeder system, and to tie the inner strand end of an active unwinding strand package to the outer strand end of a reserve package. In the parlance of the textile trade this is often referred to as "magazining". The practice of magazining has the significant advantage that manual tending of strand supplies for the feeder is substantially lessened since several strand supply packages can be arranged at spaced positions around the inlet end of the feeder with transfer tails of adjacent packages tied together as just described so that, when an active unwinding package of strand is depleted, an adjacent reserve package automatically commences unwinding without operator attention.
In order that the strand unwinding from a supply package and being advanced to a feeder can be directed to the rotating feeder tube of the feeder without being dragged over the inlet end of the tube it is customary to provide a stationary guide coaxially aligned with the tube and slightly upstream therefrom through which the supply strand advanced. Bearing in mind that the several supply packages of strand magazined for serial delivery to the feeder system are dispersed at different loci upstream of the stationary guide due to space considerations, it follows that each strand being guided from its package follows in first path from its package to the guide, and then is wrapped about the guide to move in a second path divergent to the first path. In its second path the strand moves in a course axially with and into the feeder tube. Such wrapping of the strand about the guide increases the strand tension level downstream of the guide substantially above the tension present in the strand between the supply package and the guide since the stationary guide acts as a tension generator. The increase in tension is expressed in the well known formula: EQU T.sub.2 =T.sub.1 e.sup..mu..theta.
where:
T.sub.2 =strand tension downstream of the guide PA0 T.sub.1 =strand tension upstream of the guide PA0 .mu.=coefficient of friction of the guide PA0 .theta.=wrap angle of the strand around the guide PA0 e=constant.
The tension is increased by other tensions introduced as the strand moves through the goose-neck strand feed tube and encounters frictional contact with the interior surfaces of the tube.
Drawing strandular materials over the surface of the stationary guides of the prior art is generally not detrimental to strands manufactured of isotropic materials. However, anisotropic products such as flat strands of polypropylene tape have been found to suffer adversely from such contact with the stationary guide, particularly in that the tape is caused to fibrillate or split. Bearing in mind that as the tape is pulled off over-end from its supply package for delivery to the feeder a single turn of twist is introduced into the tape for each wrap of tape pulled off the supply package, it follows that a stationary guide can act as a twist restrictor, precluding smooth advance of the twisted tape to the feeder. The twist in the tape is prevented from flowing over the surface of the stationary guide until an accumulation of turns of twist back up in the tape between the supply and the guide, whereupon the highly twisted tape is pulled over the surface of the stationary guide. In the course of such twist build-up the flat tape folds on itself, setting up longitudinal creases or fracture lines in the tape. Thereafter, when the tape is pulled over the stationary guide and/or when it is subjected to the additional frictional forces introduced as the tape is advanced through the feeder tube and laid on the feeder drum, it is susceptible to easy splitting along the fracture lines. Correlated with this is the unsatisfactory material woven from the tape. The woven material, rather than having weft possessing uniform turns of twist per unit length, has weft wherein the twist is accumulated in bunches along sections of the length of the strand.
In accordance with the present invention an inlet device or attachment is provided including guide rollers which are positioned to rotate with advance of the strand thereabout and guide the strand into the yarn storage feeder. The guide rolls have a point of tangency laying within the axial plane of the inlet end of the yarn storage feeder device. Accordingly, the yarn departs the roller at a tangent point from its guide roller and is fed into the feeder tube of the feeder without any substantial increase in tension over that existing between the supply package and the guide rolls. Since experimentation has shown that the principal cause of fibrillation of plastics tape being delivered in angular paths results from twist restriction in the advancing tape and tension build-up as the tape is advanced over a stationary guide, the present invention permits such anisotropic strandular material to be delivered without being split or fibrillated and with twist in the tape being distributed uniformly. Consequently, the disadvantages which has been shown to occur in practice with feeders of the prior art is avoided.